• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.734-738
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• 2017

In the present study, dominant factors for temperature increase and effects of mass entering the resonance tube of the gas-dynamic igniter are investigated. Using RhoCentralFoam solver in OpenFOAM program, numerical simulation is performed for three different cases. In the results, the heating of the working fluid is found to be a result from aero-thermodynamic phenomena. Appropriate mass entering to the resonance tube is found to be an important dominant factor as well.

• Journal of the Korean Society of Safety
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• v.16 no.1
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• pp.25-30
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• 2001

This paper studies the effect of vibration characteristics of tube line conveying fluid with the power steering system of bus. We modelled fluid-filled tube line using I-DEAS software to investigate vibration characteristics of the power steering tube line. And we obtained the natural frequency of tube line through finite element analysis. Analytic solutions were compared with experimental solutions to verify finite element model. We tested the tube line to examine an effect of pressure pulse by vane pump and variation of geometry of tube. From both the experimental results and the modeling results for vibration characteristics of the tube line conveying fluid, we confirmed that vibration characteristics induced by pulse propagated along the power steering tube line and resonance occurred around the natural frequency with pulse excitation.

• Journal of Energy Engineering
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• v.21 no.2
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• pp.133-137
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• 2012

Among various clean energy technologies, the solar energy technology has been widely used in various fields such as photovoltaic power generation and solar water/space heating. These days, special attention is drawn on its conversion into acoustic energy along with waste heat as a means to promote clean energy utilization. This work was carried out to investigate the possibility of converting solar energy into acoustic waves, especially, its performance characteristics for a single resonance tube (20.2 mm in ID). Variations are made for the stack length and its position as well as power supply. For a resonance tube of 200mm, an average sound pressure of 114.5 dB was measured with a stack length of 25.6mm at 5cm from the closed end. When the power supply was increased to 35W, an average sound pressure of 117.29 dB was detected with a frequency of 500Hz. There was an increase in frequency, 630 Hz (115.7dB), with a shorter resonance tube of 150mm.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.1
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• pp.34-39
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• 2002

Most X-ray generator had been used do rectifier type transformer high tension generator which is supplied in a clinical diagnosis. But it is difficult to miniaturize and become light weight. Also, because the ripple rate of tube voltage is high, X-ray generating efficiency is very low. Therefore, it is supplied gradually from abroad being developed high tension generator for inverter type X-ray generator which use semi-conductor switching element for electric power that have high speed switching ability to solved these problem. But, semi-conductor element of big capacity are used by X-ray tube's big consumption power and diffusion is difficult in the small size hospital because production cost is ascending by doing digital control through DSP and product price becomes expensive. Therefore, in this paper, design and manufactured CR type voltage divider for feedback control of tube voltage of high frequency resonance type inverter and high tension transformer for high frequency to apply economical diffusion type X-ray generator which have wide output voltage and load extent. It is Proved do X-ray generator and stability of X-ray tube's output characteristics through an experiment.

• Journal of the Korean Magnetic Resonance Society
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• v.12 no.1
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• pp.51-59
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• 2008

Convection effect in liquids has been one of the main targets to be overcome in pulsed-field-gradient NMR measurements of self-diffusion coefficients since the temperature gradient along the sample tube generated by the heating and/or cooling process causes the effect, resulting in additional diffusion. It is known that the capillary is the most appropriate tube type for diffusion experiments at variable temperatures since the narrower tube suppresses convection effectively. For evaluating the properties of hydrogen bonding, diffusion coefficients of the $K^+$-complexed and free valinomycin in a micro tube have been determined at various temperatures. From the analysis of the obtained diffusion coefficient values, we could conclude that the intramolecular hydrogen bonding in both of the $K^+$ complexed and free valinomycin in a non-polar solvent is preserved over the observed temperature range, and the temperature dependence of hydrogen bonding is more pronounced in free valinomycin. It is also thought that there is no big change in the radius of the $K^+$-complexed as temperature is varied, and the ratio of overall radius, $r_{complex}/r_{free}$ is slightly decreased as temperature rises.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.12
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• pp.622-626
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• 2001

HID(high intensity discharge)lamps are high pressure mercury lamp, high pressure sodium lamp and metalhalide lamp. metalhalide lamp among these lamps has considered to be one of the most effective artificial light sources and this lamp has good efficiency, good color rendition and good focusing capability, But the shortcorning of metalhalide lamp is known as acoustic resonance phenomena in the discharge tube when lighted by electronic ballast and then acoustic resonance cause various problems such as the arc instability, light output fluctuations. In this paper, to reduce the acoustic resonence phenomena, the electronic ballast was designed by three methods for high frequency operation wish frequency-modulated sinusodial waves in acoustic resonance frequency band. These frequency-modulated methods are resonance frequency and resonance frequency, resonance frequency and non-resonance frequency non-resonance frequency and non-resonance frequency Experiment results could't show the Presence of acoustic resonance visually and it proved that the resonance-generating conditions can be avoided by continuously changing the two operating frequencies in acoustic resonance band (20.59kHz∼94.2kHz).

• Journal of Korea Multimedia Society
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• v.18 no.4
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• pp.541-545
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• 2015

Wireless power transmission which can transmit the electrical power through the air is the promise technology. In this paper, the effects of wireless power transmission using magnetic resonance method have been studied on coil material, resonance frequency, and antenna type. We have found copper tube as a coil material had the better characteristics than that of enameled wire, and the optimal resonance frequency was 13.6MHz in the range of from 1MHz to 20MHz. And the double square spiral type antenna as a load coil was the best. The power transmission distance by magnetic resonance method with 13.6MHz was 150 cm.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.730-733
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• 2017

An ignitor for the initiation of burning propellants becomes one of the most critical components for the operation of liquid rocket engines. The important phenomenon of the igniter is thermoacoustic resonance. This paper mainly includes experimental results on thermoacoustic resonance phenomenon from distance between nozzle and resonance tube. The ultimate goal is to develop an ignitor capable of multiple ignitions based on research results about the usage of the thermoacoustic resonance phenomenon.

• International Journal of Fluid Machinery and Systems
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• v.8 no.3
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• pp.202-208
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• 2015

For a prototype turbine operating under part load conditions, the turbine output is fluctuating strongly, leading to the power station incapable of connecting to the grid. The field test of the prototype turbine shows that the main reason is the resonance between the draft tube vortex frequency and the generator natural vibration frequency. In order to reduce the fluctuation of power output, different measures including the air admission, water admission and adding flow deflectors in the draft tube are put forward. CFD method is adopted to simulate the three-dimensional unsteady flow in the Francis turbine, to calculate pressure fluctuations in draft tube under three schemes and to compare with the field test result of the prototype turbine. Calculation results show that all the three measures can reduce the pressure pulsation amplitude in the draft tube. The method of water supply and adding flow deflector both can effectively change the frequency and avoid resonance, thus solving the output fluctuation problem. However, the method of air admission could not change the pressure fluctuation frequency.

• Journal of Korean Association for Spatial Structures
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• v.2 no.1 s.3
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• pp.67-73
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• 2002

Measurement of fluctuating pressure by tube system is carefully designed due to the organ-pipe resonance. It is necessary to correct the pressure before analysis. The three method for correction the distortion fluctuation pressure short tube length and the frequency response functions and insert a restrictor in the tube to increase the damping. The first method is useful when the tube length is short. In second method, the distorted signal through the tubing transformed into the frequency domain, dividing by transfer function and inverse fourier transforming back into the time domain gives the required pressure signal. In this paper three types of tubing which have different length of 100cm, 150cm, 200cm were experimented the distorted signal and correct the distortion signal